small webrev to fix bug in hsail kernel argument logic

[Deneau, Tom]

Doug --

The small webrev
   http://cr.openjdk.java.net/~tdeneau/graal-webrevs/webrev-kernarg-fixes/webrev/

fixes some problems in the HsailKernelArguments code that caused some crashes with
certain kernel argument combinations (not any of the existing junit test cases).]

In addition added some new test cases that would have failed but now pass.

-- Tom